Hydraulic drives for extrusion press



April 5, 1960 P. BILLENM 2,931,497

HYDRAULIC DRIVES FOR EXTlUSION PRESS Filed April 3, 1957 all/[I144 /NVENTO R runs more slowly andv delivers, less water.

United States Patent-O HYDRAULIC nnrvns FOR EXTRUSION PRESS PeterBillen, Leverkusen-Kuppersteg, Germany, assignor to SchloemannAktiengesellschaft, Dusseldorf, Germany Application April 3, 1957,Serial No. 650,456 3 Claims. (Cl. 207-4) In extrusion presses,particularly those for sheathing tainers, the material that is beingextruded must always be supplied uniformly from the'two containers tothe extrusion die, as otherwise an uneven extruded product 'will result.

Extrusion presses have in the past been operated by means ofdirect-acting pumps or by means of accumulators. Operating withdirect-acting pumps has recently -fallen out of favour, asirregularities in the supply of water under pressure causes shadings inthe extruded material. The use of accumulators is therefore preferred.When operating in this way, however, with two oppositely acting pressrams, uniform working of the two rams cannot be attained, since billetsat different temperatures, or other unavoidable differences in the twocontainers, lead to different speeds of extrusion. On this grounddevices have been provided for compensating for different speeds offeed. One such device is constructed in such a way that each press ramis connected with at least one supplementary piston which reciprocatcsin a cylinder. The cylinders of the supplementary pistons on oppositesides are hydraulically connected with one another. If one of the pressrams moves in advance of the other, the supplementary piston moves withit, and forces liquid into the supplementary cylinder on the oppositeside, so that on the basis of this pressure the other ram is constrainedto overtake the lead of the first ram. The disadvantage of thisarrangement resides in the fact that the response of the device israther slugcables, with press rams hydraulically driven by pistons andacting oppositely to one another in associated congish, and that the ramencountering the higher resistance vsides of the two hydraulic pistonsth'e'two pumps of the pair having a common motor drive. In this way,

on the assumption of equal efi'iciency of the two pumps,

it is automatically ensured, that the two sides of the press willalways'receive the same quantity of liquid.

' Upon a reduction in the speed of one ram, the amount of water underpressure required by its associated cylinder diminishes, so that thesupply of water to one pump is reduced, and consequently, its motor runsmore slowly. Since, however, with this pump, the other pump acting uponthe opposite cylinder is coupled, this other pump The .result .tainersof the press.

Patented Apr. 5, 1 960 .formly. The result of this is that equally greatquantities of material are at any time extruded from both-thccon- Sincethe demand for liquid differs in. magnitude according to the profilestobe extruded, a plurality of motors are according to the inventionalways p'rovided'with two .pumps each, one' of which delivers. to oneside ofv the press and the. other to member side. The motors may beadapted .to be switched onand on at.will, in order that the quantity.necessary atlanyparticular. time may be delivered, andthZlLIlOilll'ldllE' waste of power may occur owing to the otherwisenecessary splitting ofi of a part of the pressureliquid.

When extruding, the billets must first be compressed by the press rams,before the extrusion begins. For the compression of the billets greatpressures are required. The compression should moreover proceed asrapidly as possible, whereas the speed of extrusion must in .most cases,on technical grounds,- be kept low. Now ifthe pumps acting directly uponthe press, were of such a capacity that they could effect thecompression in the short time that is desirable, the greater part ofthis capacity would be wasted during the extrusion, so that heavy idlinglosses would occur; For this reason an accumulator with a charging pumpof its own is additionally provided, the

storage capacity of which is'adequate for the entire work of compressingthe billets. The pump and the motor of the accumulator are in fact sodimensioned that they can charge up the accumulator in the time occupiedby the extrusion of the billets.

The invention, as applied to a cable-sheathing press,

is illustrated by way of example in the accompanying drawing, in which:I

1 denotes a double-billet container, having an axial longitudinal bore 2through which runs the cable to be sheathed. In the direction of thearrows 3, two billets to be extruded are introduced into the two-billetcontaincr 1. The compression of these billets by the two press rams 4and 4a then begins. These press rams are mounted on pistons 5 and 5arespectively, whichreciprocate in cylinders 6 and 6a. To the pressurespaces 7 and 7a ,of these cylinders are connected pressure supply pipes8 .and 8a, which come from a hydraulic accumulator 9. In

these pipes controllable valves 10 and 10a are provided, which areopened for the compression of the billets, and then closed again. Forthe charging of the accumulator 9 a pump 11 is employed, which drawsliquid from a reservoir through a suction pipe 12. This pump may bedriven by an electric motor 13.

Three electric motors 14, 15 and 16 are also provide'd.

The motor 14 is coupled to two hydrostatically' similar and equal pumps17 and 17a which can draw liquid from suction pipes 18 coming fromastorage tank, not shown. These pumps force liquid through deliverypipes 19 and 19a into the pressure spaces 7 and 7a of the cylinders 6and 6a respectively. Non-return valves 21 are interposed which allowliquid under pressure to pass from the pumps 17 and 17a to the cylinders6 and 6a. The motors 1s and 16.; are-.1 1. ai'similar. m nnr-,.. 11Pl ltarsu of hydrostatically similar and equal pumps 22, 22a and 23, 23arespectively. Non-return valves 20 are provided between the pumps 17, 22and 23, and non-return valves 26a between the pumps 17a, 22a and 23a, toenable the pairs of pumps to be disconnected separately. Between the twodelivery pipes 19 and 19a a safety valve 24 may be provided, which, in amanner already suggested, opens a connection between the two deliverypipes 19 and 19a when the pressure in the pipe 19a becomes greater to adefinite extent, for instance-20 percent, than the pressure in thedelivery. pipe 19, or when, in the delivery pipe 19, there is a pressuregreater to the said extent than in the delivery pipe 19a. Moreover,speed-regulating means 25' of a known kind may be provided, for thepurpose of compensating for any slight differences in the feeding speedof the pistons and 5a; for it is always possible that the pump 17a forexample, may'work with a lower volumetric efliciency than the pump l7,as a result for instance of leakage losses or bubbles of air, so thatthe deliveries differ somewhat from one another, and therefore, also thefeeding speeds of the two press rams 4 and 4a are not quite equal. Theseslight differences in speed can be compensated for, without leading toany loss of economy, by the speed-regulating means 25 allowing smallquantities of pressure liquid to escape. This device operates independence upon the speed of feed of the two press rams 4 and 4a as soonas either of these two press rams runs faster than the other. A smallquantity of liquid under pressure is then automatically let out of thepipe 19 or 19a as required, so that .the press rams 4 and 4a re-assumethe same speed. In presses the production program of which permitscertain inequalities in the feeding of the press rams 4 and 4a, thespeed regulating means 25 may be omitted. In cable-sheathing presses,however, which are particularly sensitive with respect to the uniformsupply of extruded material, such means can hardly be dispensed with.

It may be advisable to design the pumps 17 and 17a, or 22 and 22a or 23and 23a, as variable-delivery pumps. If the pumps 17 and 17a forinstance are so designed that their delivery is continuously variablethe other pumps need not be provided with any such controlling means,provided their delivery is not greater than the maximum delivery of thepumps 17 and 17a. The control devices of the pumps 17 and 17a arecoupled together, so that they always deliver the same quantities ofliquid.

Modifications of the invention are possible, by controlling the twopumps that are driven by a common motor, and work each on one side ofthe press, in dependcnce upon the difierence between the speeds of thepress rams. If for instance the press ram 4a is moving more quickly thanthe press ram 4, the pump 17a will be so controlled as to deliver less,and/or the pump 17 so as to deliver more. As means for carrying out thiscontrol, appliances known in themselves may be employed, in which atoothed rack is rigidly connected with each of the press rams 4 and 4a.These racks move in parallel paths, and have between them a pinion whichmeshes with both of them. The displacement of the axis of this pinionprovides a measure for the control of the two pumps.

I claim:

1. An extrusion press, particularly a cable-sheathing press, comprising:a container, two press rams working oppositely in the container, twohydraulic cylinders, two pistons, slidable one in each of the hydrauliccylinders, each'piston driving one of the two press rams, a hydraulicaccumulator the capacity of which is dimensioned according to theexpenditure of work required for the compression of the billets to beextruded, a charging pump delivering liquid to the accumulator,valve-controlled piping connecting the accumulator with both thecylinders on the driving side of their pistons, two similar and equalhydrostatic pumps, valve-controlled piping connecting one hydrostaticpump with one of the cylinders it .on the driving side of its pistonduring extrusion, valvecontrolled piping connecting the other pump withthe other cylinder on the driving side of its piston during extrusion,and a common motor simultaneously driving the two hydrostatic pumps.

2. An extrusion press, particularly a cable-sheathing press, comprising:a container, two press rams working oppositely in the container, twohydraulic cylinders, two pistons, slidable one in each of the hydrauliccylinders, each piston driving one of the two press rams, a hydraulicaccumulator the capacity of which is dimensioned according to theexpenditureof work required for the compression of the billets to beextruded, a charging pump delivering liquid to the accumulator,valve-controlled piping connecting the accumulator With both thecylinders on the driving side of their pistons, a plurality of pairs ofsimilar and equal hydrostatic pumps, valvecontrolled piping connectingone hydrostatic pump of each pair with one of the cylinders, andconnecting the other hydrostatic pump of each pair with the othercylinder, on the driving side of the piston in each case, and motors fordriving the hydrostatic pumps, the two pumps of each pair beingsimultaneously driven by a common motor.

3. In a cable sheathing extrusion press having a billet containerincluding oppositely facing'bores and aligned cylinder and piston meanswith each piston carrying a press ram for entry into the respectivebores for compressing a billet therein and for extruding the metalthereof for cable sheathing purposes, a driving system for said rams foractuating the same to initially compress a billet in each bore and forthereafter to move said rams with a pressure sufficient to extrude metalsimultaneously from both bores at equal speeds, said system comprising ahydraulic accumulator having a capacity suiiicient to deliver liquidunder pressure to the cylinders for moving the pistons and thus the ramsa distance sufficient to cornpress a billet accommodated in each bore,conduit means extending from the accumulator to the ends of therespective cylinders remote from the respective bores, valve meansoperably related with such conduit means for controlling liquid flowtherethrough and operable in one position to permit liquid to flow toboth cylinders to move the pistons and thus the rams a distancesufiicient to compress billets in the bores independent of anydifference in volume in the billets in the respective bores, said valvemeans then being operable in another position to cut off flow of liquidfrom the accumulator to the cylinders, said system further including atleast two similar and equal hydrostatic pumps, a conduit means extendingfrom onepump to and communicating with said remote end of one cylinder,a conduit means extending from the other pump to and communicating withthe remote end of the other cylinder, a motor operably connected withboth pumps for simultaneously driving the same, valve means operablyassociated with the respective last-mentioned conduit means to permitliquid to flow into said remote ends of said cylinders, said motor beingactuated when the first-mentioned valve means is in a position to cutoff flow of liquid from the accumulator t0 the respective cylinders,whereby billets inserted in the bores are compressed by liquid suppliedto the cylinders in common so that the respective rams move the distancerequired to compress the billet in each bore regardless of dilierencesin volume of the billets and during operation of the motor said pumpssupply equal quantities of liquid per unit of time to the respectivecylinders so that extrusion from the respective bores is effected by therams moving at the same speed so that the same quantities of billetmetal are extruded from the respective bores and the system furtherincluding a charging pump for delivering liquid to the accumulator andmeans for actuating said charging pump during the interval that thefirst-mentioned valve means is in a position to block the flow of liquidfrom the accumulator to the cylinders so that the accumu- Iator can berecharged during extrusion, so is to be available for a subsequentbillet compressing operation.

References Cited in the file of this patent UNITED STATES PATENTSRobertson Apr. 17, 1883 Whitney Feb. 2, 1886 Gabriel Mar, 8, 1927Lofiier 6, 1927 8 Summey iuly 1, 1930 Cannon July 4, 1939 Peterson Mar.19, 1940 Norman Feb. 26, 1957 Govan et al Mar. 25, 1958 FOREIGN PATENTSGreat Britain Oct. 12, 1955 Germany Aug. 23, 1956 Great Britain Mar. 27,I957

